Electron discharge device grid having parallel cross straps connected at the center thereof



April 2, was

G. MIALE ETAL ELECTRON DISCHARGE DEVICE GRID HAVING PARALLEL CROSSSTRAPS CONNECTED AT THE CENTER THEREOF Filed June 24, 1965 FIG.3.

6O so FIGS WITNESSES f/M 4M4 INVENTORS Goliurdo Miole 81 Edward R.Compognu ATTbRNEY III Patented Apr. 2, 58

fiice 3,376,462 ELECTRON DISCHARGE DEVICE GRID HAVING PARALLEL CROSSSTRAPS CONNECTED AT THE CENTER THEREOF Goliardo Miale and Edward R.Campagna, Bath, N.Y.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., acorporation of Pennsylvania Filed June 24, 1965, Ser. No. 478,002 7Claims. (Cl. 313350) ABSTRACT OF THE DISCLOSURE This invention relatesto a frame grid type of electrode for an electron discharge deviceincluding a pair of side rods disposed in a substantially parallelrelation, a plurality of grid wires disposed between and supported bythe pair of side support rods, and at least one pair of frame strapsdisposed between and secured on both sides of the side support rods.More particularly, the frame straps are so shaped that a portion of oneframe strap may be connected to a portion of the other frame strap andthat the frame strap is withdrawn from the surface of an adjacentlydisposed electrode.

This invention relates to electron discharge devices and morespecifically to improvements in electrode structures therefor.

In those applications of electron discharge devices where the device isbeing operated at high frequencies and/or at low noise levels, thespacing between a cathode element and a lateral grid wire of a controlor first grid electrode of this device must be made smaller and withgreater precision than in other electron discharge devices. If thespacing between the cathode element and the grid electrode is notaccurately controlled, a great difference in the performance ofsimilarly designed electron discharge devices will be obtained whenproduced by mass production methods. The transconductance of suchdevices in general varies as a function of the spacing between thelateral grid wires of the control grid element and the surface of thecathode element; therefore, this spacing should be made as small aspossible and must be accurately set if a product having improved,uniform characteristics is to be manufactured.

Another difiiculty in the production of high performance electrondischarge devices results from the necessity of providing a grid elementhaving a greater number of turns per inch of the lateral grid wire andof using a very thin lateral grid wire. In the ordinary type of gridelement structures, there are no means to establish an accurate andrigid spacing between the side support rods upon which the lateral gridwire is suspended. Also as a greater number of turns per inch of lateralgrid wire is used, it is necessary to reduce the wire diameter to amagnitude as low as .3-.5 mils. Thus as the wire diarneter becomessmaller and the turns per inch greater, the tension exerted upon the twoseparated, non-rigid side rods becomes great enough to physically bendthe side rods. This in turn distorts the shape of the finished grid,which will make it difficult if not impossible to provide the desireduniform cathode to grid distance.

A possible solution of this problem has been the utilization of a frametype support structure upon which the fine lateral grid wire may besuspended. Typically, such frame structures consists of two support rodswhich are interconnected rigidly with a plurality of members or straps.It is noted that such structures may be formed as by stamping out aunitary member or by welding the individual straps to the side supportrods. In either case, a

rigid structure is provided about which the fine lateral grid wire maybe disposed.

Such a grid electrode structure has been more thoroughly described in acopending application, entitled Assembly of Electrodes with Aligned GridWires for Electron Discharge Devices, by Goliardo Miale and Anton vander Jagt, Ser. No. 438,272, and assigned to the assignee of thisinvention. More specifically, this copending application describes agrid structure commonly known as half frame grids comprising a pair ofside support rods, a strap disposed on one side of said support rods,and a plurality of lateral grid wires disposed and suspended upon theother side of the side support rods. One of the many advantages of thisstructure is that the lateral grid wires of this structure may bepositioned within .001 to .0015 inch of an adjacent electrode withoutinterference from the strap which rigidly supports and spaces the sidesupport rods from each other. Though the desirability of maintaining anaccurate and small spacing between the cathode element and a controlgrid electrode has been noted above, the copending application fullydiscusses the advantages of maintaining an accurate spacing between afirst or control grid electrode and a second or screen grid electrodeor" half-frame variety. Specifically, it has been verified that bymaintaining a minimum distance between the first grid electrode and asecond grid electrode that the number of electrons absorbed by thesecond grid electrode and as a result the noise figure of the electrondischarge may be significantly reduced. As further shown in theabove-mentioned copending application, half-frame grids are incorporatedinto a tetrode electron discharge device as the second grid electrodes.A principal advantage of the half-frame grid structure is that it may bepositioned very close to an adjacent element. In ordinary full framegrid structures, sup port straps are placed on either side of the sidesupport rods and as a consequence may contact an adjacent elementthereby limiting the spacing between this element and the gridstructure. However, by placing the straps on only that side of the sidesupport rods remote from the lateral grid wires, the lateral grid wiresmay be spaced at extremely close distances from the adjacent element.

However, when attempts were made to wind half-frame grid structures witha turns per inch of lateral grid wire in the order of 300' to 400, itwas discovered that a portion of the laterial grid wires were onlyloosely suspended between the side support rods. Upon furtherinvestigation, it was found that the side support rods had a tendency torotate under the influence of the winding of the lateral grid wires dueto the lack of a supporting strap on both sides of the grid electrodestructure. As more fully explained in the above-mentioned copendingapplication, the frame grid electrodes are formed by rotating the sidesupport rods as by a grid lathe and by continuously moving the electrodegrid structure as the lateral grid wire is being fed onto and woundabout the side support rods. The result of the revolving action was toprovide loose lateral grid wires in the initial stages of the windingdue to the increasing tension placed upon the side support rods by thelateral grid wire as the process of the winding is continued. Thus,those lateral grid Wires that are wound upon the grid electrode at theend of the winding process are placed under great tension, while thoselateral grid wires initially wound are loosely supported upon the sidesupport rods.

Typically at the end of the manufacturing process, each of the electrondischarge devices are subjected to a microphonic test which detects thehigh frequency vibration of the lateral grid wires while the tube isbeing mechanically shocked. The results of this test may be observed ona monitoring or scope device as a fluctuation in the plate current; thelooser the lateral grid wires, the greater the signal recorded and thelonger it takes for this signal to subside. Further, it may be wellunderstood that loosely suspended lateral grid wires may be easilydeformed so as to effect differences in the spacing between the lateralgrid wire and an adjacent electrode and thereby produce differentparameters between each of the electron discharge devices.

Accordingly, it is the general object of this invention to provide a newand improved electron discharge device.

It is another object of this invention to provide an improved electrondischarge device wherein the lateral grid wires of a grid electrode aresecurely supported and spaced with respect to adjacent elements of thedevice.

It is a further object of this invention to provide a new and improvedelectrode grid structure wherein the side support rods are securelypositioned with respect to each other.

It is another object of this invention to provide an improved electrodegrid structure which can be wound with high turns per inch of lateralgrid wires under high tension without a deformation of either the sidesupport rods or the lateral grid wires.

A still further object of this invention is to provide an improvedelectrode grid structure for an electron discharge device wherein theside support rods are rigidly spaced and supported from each otherwithout mechanical or electrical interference with adjacent elements ofthe electron discharge device.

Briefly, the present invention accomplishes the abovecited objects byproviding an improved electron discharge device, wherein there isincorporated an electrode structure having support members or strapsfixedly disposed on either side of the side support rods. Further, aportion of the straps disposed on either side of the side support rodsis securely attached to the strap disposed upon the other side of theside support rods to thereby provide a structurally rigid structure. Inaddition, it is desired to form that strap in proximity to an adjacentelement of the electron discharge device so that the strap issubstantially removed from the surface of the adjacent element. In oneparticular embodiment of this invention, the support members or strapsdisposed on either side of the side support rods are each shaped andattached to form a structure having an X configuration. In analternative embodiment, that strap in proximity to the adjacent elementis so bent or formed that a portion thereof may be attached to thatstrap upon the opposite side of the side support rods which retains itslinear shape.

Further objects and advantages of the invention will become apparent asthe following description proceeds and features of novelty whichcharacterize the invention will be pointed out in particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of the invention reference may be had to theaccompanying drawings, in which:

FIGURE 1 shows a partially sectioned view of an electron dischargedevice in which this invention has been incorporated;

FIG. 2 shows an isometric view of an electrode as sembly which has beenincorporated in the electron discharge device of FIG. 1;

FIG. 3 shows a plan view of the grid electrode structure of thisinvention and an adjacent element which may be incorporated into theelectron discharge device of FIG.

FIG. 4 shows a side view of the grid electrode structure shown in FIG.3; and

FIG. 5 shows a plan view of an alternative embodiment of the gridelectrode structure and an adjacent element which may be incorporated inthe electron discharge device of FIG. 1.

Referring now to the drawings and in particular to FIG. 1, there isshown an electron discharge device employing the present invention inits preferred form. The electron discharge device 10 is comprised of anenvelope 12 made of a suitable material such as glass with an electrodeassembly indicated generally by the character 24 enclosed therein. Theenvelope 12 shown is of conventional design includes a tipped offexhaust 13 on top of the envelope 12 and a button stem header 14 closingoff the bottom portion of the envelop 12. A plurality of electricallyconductive terminals or lead elements 18 are sealed through the header14 and are connected to the elements of the electrode assembly 24 by theinterconnecting leads 16. The terminals 18 not only supply the necessaryvoltage to the elements of the electrode assembly 24, but also act inconjunction with a pair of insulating elements 20 and 22 to support theelectrode assembly 24 within the envelope 12.

Referring now to FIGS. 1 and 2, the electrode assembly 24 includes anelectron emissive element or cathode 26 of the indirectly heated typewhich extends through and is supported in apertures 27 and 29respectively of the insulating elements 22 and 20. A folded heaterelement 38 is disposed within the cathode 26 to energize a layer 56 of asuitable electron emissive material such as one of the barium strontiumcarbonate. A pair of grid electrodes 32 and 30 are disposed on eitherside of and in planes parallel to the cathode 26. The grid electrodes 30and 32 are of the half-frame variety and are comprised of (see alsoFIGS. 3 and 4) side support rods or side members 40 which are spaced andsupported in a parallel relationship from each other by support membersor cross straps 46 and 48. Upon that side of the grid electrodes 30 and32 adjacent the cathode 26, there is fixed to the side sup port rods orside members 40 a plurality of lateral grid wires 44 disposed in asubstantially parallel relationship to each other. It is noted that nolateral grid wires 44 are disposed upon the other side of the gridelectrodes 30 and 32. Further, the side rods 40 of the grid electrodes30 and 32 are mounted within apertures 41 within the spacer elements 20and 22.

Two substantially planar anode elements 34 and 36 (see FIG. 1) aredisposed in planes parallel to and on either side of the grid electrodes30 and 32 respectively. The anode elements 34 and 36 are supported bythe spacer elements 20 and 22; more specifically, each of the anodeelements 34 and 36 have tab portions which extend through slots 52 ofthe spacer elements 20 and 22. As, shown in FIG. 2, the side rods 40 maybe secured to the spacer element 22 as by stops 54 which are attached tothe side rods 40 as by welding. It may be understood that the straps 46and 48 directly abut against one side of the spacer element 22 and thatthe stops 54 abut against the other side of element 20 to therebysecurely mount the grid electrodes 30 and 32 upon the spacer element 22.

In one exemplary embodiment of this invention, the anode elements aremade of an aluminum clad steel. Further, the grid element comprises apair of side rods made of molybdenum and having a diameter of .0305inch, and frame straps made of molybdenum for maintaining the side rodsspaced at a distance of .200 inch. A plurality of lateral grid wiresmade of tungsten and having a diameter of .0004 inch is wound with aturn per inch of 413 about a section of the side rods .320 inch long.The frame straps are disposed .364 inch from each other and are securelyattached to the side rods as by welding.

As disclosed in the above-mentioned copending application, the gridelements may be manufactured by first forming a ribbon including a pairof side rods rigidly spaced from each. other by the frame straps, andthen winding the lateral grid wires thereabout as upon a grid lathe. Inorder to eliminate the waste of removing the lateral grid wires from oneside of the ribbon to form the half-frame grid, it is suggested that tworibbons may be wound simultaneously thereby disposing a single set ofgrid wires upon only one side of each ribbon. After the winding process,the ribbons may be separated as by cutting the lateral grid wiresjoining the ribbons together. Further, lateral grid wire may be furtherconserved if the the ribbons are offset from each other so that theframe straps do not directly abut against each other but instead lieupon the side rods of the opposite ribbon.

As shown in FIGS. 3 and 4, the grid electrodes of this invention havebeen designed to be placed at a minimum distance from an adjacentelement such as the cathode 26, while supporting the side rods 40rigidly with respect to each other. In particular, a portion of thesupport members or straps 46 and 48 intermediate the side rods 40 aresecurely attached to each other. In a preferred embodiment of thisinvention, the portions of each of the straps 46 and 48 are secured toeach other as by spot welding. In the alternative, the portions of thestraps 46 and 43 could be attached as by a clip 50. Further as shown inFIG. 3, the strap 48 has been so shaped so as to prevent any mechanicalor electrical interference with the adjacent element (i.e. cathode 26).Specifically, the strap 48 has been bent inward and away from thesurface of the adjacent element so as to provide a greater spacing Abetween the grid electrode and the adjacent element. The straps of aregular or full frame grid must be spaced at a greater distance from theadjacent cathode because of the thickness of these straps. It has beenfound that the maximum grid electrode strength is obtained when theshape of the straps approaches that of an X (see FIG. 3). In addition,the bent or curved straps 46 and 48 may make it possible for such a gridelectrode to be spaced from an adjacent element by distances as small as.001 inch to .0015 inch.

Although the above explanation and drawings have been directed to thatcase where a grid electrode is spaced from a cathode, it is pointed outthat the grid electrode of this invention could likewise be spaced at aminimum distance from another grid electrode. As disclosed in theabove-mentioned copending application, a half-frame grid electrode couldbe spaced at a close distance from a first or control grid therebyassuring that the current absorbed by the second half-frame grid and thenoise factor are minimized. It is noted that the half-frame grid of thisinvention could be easily incorporated into the electrode assembly ofthe copending application as a second or screen grid electrode. Further,the specific method as disclosed in the above-mentioned copendingapplication of winding the lateral grid wire about the side support rodsto insure the accurate alignment of the active portions of the gridlaterals of adjacent grid electrodes could likewise be adapted to windthe grid wire upon the side support rods of the electrode structure ofthis invention.

Referring now to FIG. 5, an alternative embodiment of this inventionwill be described. This electrode structure comprises a pair of sidesupport rods 6t) which are disposed and supported in a parallelrelationship by straps 66 and 68 which are in turn secured upon oppositesides of the support rod 60 as by welding. Further, a portion of thestraps 66 and 68 intermediate the side rods is secured as by welding orin the alternative by a clip 79. A plurality of lateral grid wires 67are disposed in a plane and suspended from the side rods 60. As shown inFIG. 5, the curvature of the strap 68 may be varied to provide greaterclearance or spacing between the straps 68 and the surface of anadjacent element (i.e. cathode 26).

While there has been shown and described what is at present consideredto be the preferred embodiment of this invention, modifications theretowill readily occur to those skilled in the art. It is not desired,therefore, that the invention be limited to the specific arrangemensshown and described and it is intended to cover in the appended claimsall such modifications as fall within the true spirit and scope of theinvention.

We claim as our invention:

1. An electrode for an electron discharge device comprising a pair ofside rods disposed in a spaced apart relationship to each other, aplurality of uniformly spaced grid wires extending between and supportedupon said side rods, and a pair of straps extending between and attachedto said side rods, each of said straps having a portron secured to aportion of the other strap to provide a rigid structure.

2. An electrode for an electron discharge device comprrslng a pair ofside rods held in a spaced apart relat onship by a pair of frame strapsextending between said side rods, each of said side rods disposedbetween and attached to said frame straps, and a plurality of lateralgrid wires extending between and supported upon said side rods, aportion of each of said frame straps secured to a portion of the otherframe strap.

3. A frame type grid electrode for an electron discharge devicecomprising a pair of side rods held in a substantially parallel andspaced apart relationship to each other by two pairs of frame strapsextending between and positioned at either end of said side rods, eachof said side rods disposed between and attached to each of said framestraps, and a plurality of lateral grid wires disposed in a uniformlyspaced relation between said two pairs of frame straps, said pluralityof lateral grid wires extending between and attached to said side rods,each of said pairs of frame straps having a frame strap with a portionthereof secured to a portion of the other frame strap.

ft. An electrode for an electron discharge device comprising a pair ofside rods held in a spaced apart relationship from each other by a pairof straps extending between and supporting said side rods, each of saidside rods disposed between and secured to said frame straps, and aplurality of grid wires extending between and supported in a plane bysaid side rods, said straps being so formed as to be withdrawn from saidplane and to allow a portion of each of said straps to be attachedtogether.

5. An electron discharge device comprising a first and second electrode,said first electrode including a pair of side rods held in a spacedrelationship from each other by a pair of straps extending between andattached to said side rods, and a plurality of lateral grid wiresdisposed between and suspended from said side rods, said secondelectrode having a surface disposed adjacent said first electrode, saidstraps being so formed as to be withdrawn from said surface and to allowa portion of each of said straps to be attached together.

6. An electron discharge device comprising a first and second electrode,said first electrode including a pair of side rods held in spacedrelationship by a first and second strap each extending between andattached to said side rods, and a plurality of uniformly spaced lateralgrid wires disposed between and suspended from said side rods, saidsecond electrode having a surface disposed adjacent said first Strap ofsaid first electrode, said str-aps being shaped that a portion of saidfirst strap is secured to said second strap and that said first strap isrecessed from said surface to thereby allow said first and secondelectrodes to be closely spaced from each other.

7. An electrode for an electron discharge device c0mprising a pair ofside rods held in a substantially parallel, spaced apart relationshipwith each other by a pair of frame straps extending between andsupporting said side rods, said side rods disposed between and attachedto said frame straps, and a plurality of lateral grid wires extendingbetween and suspended upon said side rods, said frame straps beingshaped in an X configuration and having portions thereof securelyattached to each other.

References Cited UNITED STATES PATENTS 3,258,637 6/1966 Schiekel 3l3350JOHN W. HUCKERT, Primary Examiner. A. J. JAMES, Assistant Examiner.

